In the packaging industry, it is often useful to bundle individual articles into groups of such articles. For example, when one buys bottled water at a supermarket, it can be purchased either one bottle at a time, or in shrink-wrapped units that contain a rectangular array of bottles. These arrays come in various sizes and shapes.
A difficulty that arises is that of forming these bundles from a stream of packaging units that move steadily along a conveying direction. In general, it is useful to speak of the rows and columns of a product group. The rows extend along the conveying direction, whereas the columns extend perpendicular to the conveying direction.
Forming the rows is fairly straightforward. One simply passes the packaging units through lane dividers to form single streams. However, forming the columns is more complicated. This complexity arises in part because the containers are moving all the time and must somehow be divided off from each other while they are moving.